Hyatt.] 18 [May 20, 



52 mm. D'Orbigny's types agree with this identification. One 

 specimen from the lower part of the same zone with Liassicus is 

 named moreanus, and may be said to agree with D'Orbigny's figure. 1 

 This is simply a variety identical with colubratus Zeit., growing to a 

 larger size than catenatus. 



At the diameter of 168 mm. in this specimen, the pilae crossed the 

 abdomen, showing that old age had set in. That this is sometimes an 

 embryonic feature retained throughout life is shown by another speci- 

 men, which at the diameter of 21 mm. has the ribs continued over 

 the abdomen. The typical angulatus form occurs as in Germany, in 

 the true Angulatusbed, above the catenatus and moreanus varieties. 

 The stout form of Charmassei occurs at Semur in the same bed, but 

 the more compressed and more involute form which passes into Leig- 

 neletii occurs in the Scipionianus zone, and also in the BucHandi 

 zone. In the latter it is associated with a very thin form which 

 seems to be a transition to Boucaultianus, and is identical with Char- 

 massei D'Orbigny figured in PI. 92, figs. 1, 2. One of these, 375 mm. 

 in diameter, had the pilae quite prominent on the abdomen. 



The true Boucaultianus occurs above the Bucklandibed, associated 

 with Birchii. 



Amm. subangularis Oppel, in the Munich Museum, from Kaltenthal, 

 has young like planorbis, but the pilae in one specimen cross the abdo- 

 men. Another from Filder has smooth abdomen until it is an inch 

 in diameter, then the pilae cross the abdomen. One from Hammerk- 

 har seems to pass through this stage, and finally becomes channelled, 

 as in angulatus. In old age the abdomen continues smooth, and the 

 shell resembles the old stage of Caloceras Johnstonl This is hardly 

 an intermediate form, and does not confirm the evidence brought for- 

 ward by Prof. Quenstedt, which is founded upon the occurrence of 

 similar abnormal forms, though the conclusions of that sagacious 

 author are in the main correct. It seems to me, indeed, to be merely 

 a reversionary form of planorbis or Johnstoni. 



Waagen's name iEgoceras is retained for this group on account of 

 the resemblance of the extreme young of angulatus to the figure 

 which he gives of the type of his genus, jEgoceras Buonarotti of the 

 Muschelchalk. He and Mojsisovics concur in describing the extreme 

 young of Amm. incultum as similar to planorbis. If this is really so, and 

 Palrrmi and planorbis, etc., are as nearly related as they appear to be by 



* The original in the Jardin des Plantesiis a fragment. It is like the figure, hut 

 shows that the interior whorls have been almost wholly restored. 



